linux-kernel - Re: [PATCH] mmc: core: add auto bkops support

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Message-ID: <576B7211.2030208@intel.com>
Date:	Thu, 23 Jun 2016 08:22:25 +0300
From:	Adrian Hunter <adrian.hunter@...el.com>
To:	Shawn Lin <shawn.lin@...k-chips.com>,
	Alex Lemberg <Alex.Lemberg@...disk.com>,
	Ulf Hansson <ulf.hansson@...aro.org>
Cc:	Jaehoon Chung <jh80.chung@...sung.com>,
	"linux-mmc@...r.kernel.org" <linux-mmc@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Doug Anderson <dianders@...omium.org>,
	"linux-rockchip@...ts.infradead.org" 
	<linux-rockchip@...ts.infradead.org>
Subject: Re: [PATCH] mmc: core: add auto bkops support

On 23/06/16 04:33, Shawn Lin wrote:
> 在 2016/6/22 22:08, Alex Lemberg 写道:
>> HI Shawn,
>>
>> On 6/21/16, 4:44 AM, "Shawn Lin" <shawn.lin@...k-chips.com> wrote:
>>
>>> On 2016/6/20 21:33, Alex Lemberg wrote:
>>>> Hi Shawn,
>>>>
>>>> […]
>>>>
>>>>>>> +
>>>>>>> +static int mmc_stop_auto_bkops(struct mmc_card *card)
>>>>>>> +{
>>>>>>> +    int err = 0;
>>>>>>> +
>>>>>>> +    if (!card->ext_csd.auto_bkops_en)
>>>>>>> +        return 0;
>>>>>>> +
>>>>>>
>>>>>> Shouldn’t the BKOPS_STATUS be checked prior to disabling the BKOPS
>>>>>> activity of the device?
>>>>>>
>>>>>
>>>>> Hrmm.. I read the whole section of spec for it, and I did find this
>>>>> requirement for manul bkops but not for the auto one. So what should we
>>>>> do if using the auto one?
>>>>>
>>>>
>>>> In case of AUTO BKOPS, the eMMC Device should perform internal GC
>>>> in the same way as in case of MANUAL BKOPS.
>>>> The only difference is a host awareness.
>>>
>>> agree.
>>>
>>>> Although there is no requirement in the spec, I think the driver can
>>>> give some time to the device to perform/complete its internal GC during
>>>> the idle time.
>>>> Thus I think we can check the BKOPS_STATUS on Runtime suspend.
>>>
>>> We shouldn't diable bkops on *runtime* suspend as it's just the right
>>> time for firmware to do GC. We could consider to check and wait for
>>> the status when doing poweroff, although it seems firmware should be
>>> able to accept the disable cmd and deal the on-going work perfectly
>>> when doing bkops without host's awareness, just the same way as suddent
>>> power loss cases.
>>
>> If I am not wrong, in current implementation of runtime suspend,
>> the driver stops BKOPS (send HPI) just before sending sleep command,
>> see _mmc_suspend(), depends on “MMC_CAP_AGGRESSIVE_PM” flag.
>> In this case, the eMMC device will not have enough time to perform internal
>> BKOPS in both – Manual and Auto BKOPS configurations.
>>
> 
> ye, so it seems a pre-exiting issue before introducing auto bkops?
> I think we can push another patch to improve it but not handling
> it for this $SUBJECT, does it sound ok to you?

Runtime suspend for eMMC has a default auto-suspend delay of 3 seconds
(refer mmc_blk_probe()).  Isn't that when auto bkops would happen?

> 
>> For the poweroff, it should be OK with a current implementation of
>> PON (mmc_poweroff_notify())
>>
>>>
>>> Also I don't know whether the firmware will reflect its status on
>>> BKOPS_STATUS or not when enabling the auto one. I will do more test.
>>>
>>> Anyway, thanks for sharing your thought.
>>> Also Adrian point out that currently we trigger manual bkosp from
>>> userspace via mmc-utils, and I agreed we shouldn't force kernel stack
>>> to enable it defaultly. So I'm prone not to update this $SUBJECT and
>>> migrate it to mmc-utils later.
>>>
>>>>
>>>> […]
>>>>
>>>> Thanks,
>>>> Alex
>>>>
>>>
>>>
>>> -- 
>>> Best Regards
>>> Shawn Lin
>>>
>>
> 
>